Motor graders are used primarily as finishing tools to sculpt a surface of a construction site to a final shape and contour. Typically, motor graders include many hand-operated controls to steer the wheels of the grader, position a blade, and articulate a front frame of the motor grader. The blade is adjustably mounted to the front frame to move relatively small quantities of earth from side to side. In addition, the articulation of the front frame is adjusted by rotating the front frame of the grader relative to the rear frame of the grader.
One example of a motor grader and a mechanism for positioning a blade of the motor grader is provided in U.S. Pat. No. 8,103,417 issued to Gharsalli et al. (the '417 patent) on Jan. 24, 2012 entitled Machine with Automated Blade Positioning System. The '417 patent discloses a motor grader having a frame to which a drawbar-circle-moldboard (DCM) assembly is mounted. A drawbar is connected to the frame by a ball and socket joint. A pair of double acting hydraulic rams connected between the frame and the drawbar affect vertical movement of the DCM assembly, and a side shift cylinder connected between the drawbar and a link bar adjustable between a plurality of predefined positions affects horizontal movement of the DCM assembly. A circle assembly may be connected to the drawbar by a motor to drivingly support a moldboard assembly having the blade and blade positioning cylinders. The DCM assembly may be controlled to rotate the circle assembly and the moldboard assembly relative to the drawbar, and the blade may be movable horizontally and vertically and oriented relative to the circle assembly via blade positioning cylinders.
To produce a final surface contour, the blade and the frame may be adjusted to many different positions. As may be apparent from the '417 patent, positioning the drawbar and the blade of a motor grader is a complex task that may require information regarding the status and position of many components of the DCM assembly. The information may be used by the operator and/or a controller to ensure that the drawbar and the blade are correctly positioned to produce the desired contour, and to adjust the drawbar and the blade if they are not in the correct position.